A man in Illinois thought to have contracted the MERS virus has been found to be clear of the viral infection.

The man was suspected of contracting MERS after coming in contact with a healthcare worker from Indiana who has been confirmed to have the MERS virus and hospitalized. Both men had met on two occasions, had shaken hands with each other and spent over 30 minutes in close proximity. When the man from Indiana ended up in the hospital with a confirmed case of MERS infection, the man from Illinois was brought in for precautionary testing. He displayed no symptoms at the time.

He underwent a series of blood tests meant to determine if any antibodies were present in his blood. Antibodies are produced by the body’s immune system in response to the introduction of a foreign object to the body, in this case a virus. Early tests revealed some possible signs of immune system activity. On May 17, his case was announced as possibly the first transmission of the virus between humans in the United States.

Though not much is known about the virus, it does appear that the virus does not transmit easily between humans. MERS is thought to have originated in other mammals, such as camels, from which humans have contracted the virus.

Later tests revealed that the man from Illinois was actually clear of the virus and the CDC made their announcement, officially removing him from the list of MERS cases being reported worldwide. The man from Indiana is recovering and is no longer being hospitalized.

So far, the World Health Organization has recorded 635 test confirmed cases of MERS globally. 562 of these cases have been reported in Saudi Arabia, where the outbreak originated. Of these cases, 193 have proven fatal worldwide. 180 of these deaths occurred in Saudi Arabia. The virus has now reached 20 countries.

A combination of our lack of understanding of the virus and the high mortality rate have led health officials to take an overly cautious approach to those suspected to have been exposed to the virus. According to the CDC, that is why the man from Illinois was brought in for testing and treatment despite his lack of outward symptoms and the difficulty of contraction between humans.